Stalagmites provide view of abrupt climate events (Image 9)

Georgia Institute of Technology researchers Stacy Carolin, Kim Cobb, Eleanor Middlemas, Jessica Moerman and Danja Mewes, and caving guide Jenny Malang, stand at the entrance to Cobweb Cave in Gunung Mulu National Park, Borneo. The researchers were part of a Georgia Tech team that created a new set of long-term climate records based on their findings from cave stalagmites collected in Borneo.
New climate records by researchers at Georgia Tech show that the western tropical Pacific responded very differently than other regions of the world to abrupt climate change events. Their findings suggest that climate feedback within the tropical regions may amplify and prolong abrupt climate change events that were first discovered in the North Atlantic. The 100,000-year climate record adds to data on past climate events, and may help scientists assess models designed to predict how the Earths climate will respond in the future.
For the study, the researchers performed oxygen isotope analysis on more than 1,700 calcium carbonate samples taken from four stalagmites found in three different northern Borneo caves. The ratio of oxygen isotopes contained in the calcium carbonate samples is set by the ratio of oxygen isotopes in rainfall at the site because the rainwater seeps in the ground, dissolving the limestone rock and dripping into caves to form stalagmites. Stalagmites form at a rate of roughly 1 centimeter every thousand years.
"To my knowledge, this is the first record that so clearly shows sensitivity to one set of major abrupt climate change events and not another," said Kim Cobb, an associate professor in the School of Earth and Atmospheric Sciences at Georgia Tech. "These two types of abrupt change events appear to have different degrees of tropical Pacific involvement, and because the tropical Pacific speaks with such a loud voice when it does speak, we think this is extremely important for understanding the mechanisms underlying these events."
The research was supported by a National Science Foundation Presidential Early Career Awards for Scientists and Engineers (PECASE) award (ATM 06-45291).
(Date of Image: Fall 2012)
Credit: Syria Lejau, Gunung Mulu National Park